Abstract

This paper reports results of an extensive Monte Carlo simulation analysis
on the impact of DP-QPSK pulse shape in high-spectral efficiency WDM
transmission at 112 Gb/s per channel. The pulse shapes studied include NRZ,
50% duty cycle RZ and 67% duty cycle RZ. Both symbol-aligned and
symbol-interleaved formats are investigated and compared for nonlinear
transmission tolerance on common dispersion maps used in terrestrial
long-haul systems. The RZ pulse shape shows the greatest improvement in
nonlinear tolerance with symbol-interleaving. However, symbol-interleaving
only provides significant benefit in optical line systems designed to
preserve the pulse shape during transmission, such as systems based on
distributed dispersion compensating fiber (DCF). The duty cycle of the RZ
pulse has only a minor impact on nonlinear performance, and even systems
based on the NRZ pulse shape can gain significant benefit from
symbol-interleaving.